Medical injection device

ABSTRACT

The present invention relates to an injection device ( 1 ) for setting and injecting set doses from a held drug cartridge ( 10 ). The injection device ( 1 ) comprises a housing ( 110, 120, 130, 140 ), a piston rod ( 800 ), a rotatable driver ( 500, 700 ) and a dose control member ( 350 ). A stored energy source ( 560 ) is configured to drive rotation of the driver ( 500, 700 ) to cause the piston rod ( 800 ) to expel a set dose. The dose control member ( 350 ) rotates during dose setting and during dose expelling. A first clutch (C 1 ) is arranged between the dose control member ( 350 ) and the driver ( 500, 700 ). A second clutch (C 2 ) is arranged between the driver ( 500, 700 ) and the housing ( 110, 120, 130, 140 ) to control the expelling movement. During dose setting the first clutch (C 1 ) is disengaged and the second clutch (C 2 ) is engaged. During dose expelling the first clutch (C 1 ) is engaged and the second clutch (C 2 ) is disengaged.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a 35 U.S.C. § 371 National Stage application ofInternational Application PCT/EP2013/055450 (published as WO2013/156224), filed Mar. 15, 2013, which claimed priority of EuropeanPatent Application 12165081.6, filed Apr. 20, 2012 and European PatentApplication 12165082.4, filed Apr. 20, 2012; this application claimspriority under 35 U.S.C. § 119 of U.S. Provisional Application61/638,766; filed Apr. 26, 2012 and U.S. Provisional Application61/638,565; filed Apr. 26, 2012.

The present invention generally relates to medical injection devicesadapted for managing medical therapy. In particular, the inventionrelates to medical injection devices adapted to provide ease of use in acost-effective way.

BACKGROUND OF THE INVENTION

In the disclosure of the present invention reference is mostly made tothe treatment of diabetes by delivery of insulin, however, this is onlyan exemplary use of the present invention.

Conventional delivery devices for delivery of liquid drugs by means ofsubcutaneous injection typically have been provided as devices such aspen-shaped devices having a cylindrical form-factor. The cylindricalform-factor approach has mainly been chosen due to the particular use ofcylindrical drug-filled cartridges. While the cylindrical form-factorgenerally enables design of slim devices, this form-factor typically hasshort-comings as regards device length and available surface area forpresenting information to the user, e.g. by means of a display.

To overcome these problems, delivery devices having form-factors otherthan the pen-shaped form-factor have been proposed. Examples ofinjection devices having both the cylindrical form-factor as well asdevices having a non-cylindrical form factor are disclosed in WO98/10814.

Generally, from a users viewpoint there is a wish that the deliverydevice is as slim and short as possible in order to provide for acompact device which may be easily carried about, i.e. in a shirt-pocketor the like. At the same time, there is a wish that modern injectiondevices offer an increasingly variety of features. Such features mayinclude a large display for presenting the size of the set dose, a largemaximum dosing amount available for each single administration,automatic expelling of set doses, the prevention of setting a doseexceeding the drug amount remaining in the device, etc.

In a recent publication, WO 2011/045611 discloses a spring driveninjector having a dose setting arrangement to select a dose volume and adrive mechanism which in some forms include a preloaded spring havingstored energy sufficient to expel the entire useable contents of acartridge over a succession of doses. In accordance with the teachingsof WO 2011/045611 the proposed injection devices presents drawbackshaving regard to building length. In addition, the proposed windowarrangement for indicating set doses provides a far from user friendlydesign as it includes a window that rotates relative to the housing asthe dose is being dialled. Furthermore, potentially unsafe situationsmay occur if a mechanical defect should occur within the device causingan uncontrolled expelling of the entire contents of the cartridge.

Having regard to the above discussion, it is a first object of thepresent invention an injection device that is superior in userfriendliness compared to prior art devices.

It is a further object of the present invention to provide an injectiondevice that is more compact than prior art devices.

It is a still further object of the present invention to provide amedical injection device that is safer in use compared to prior artinjection devices.

DISCLOSURE OF THE INVENTION

In the disclosure of the present invention, embodiments and aspects willbe described which will address one or more of the above objects orwhich will address objects apparent from the below disclosure as well asfrom the description of exemplary embodiments.

Thus, in a first aspect of the invention a medical injection device forsetting and injecting set doses from a held drug cartridge is provided,where the medial injection device comprises:

-   -   a housing,    -   a dose setting arrangement including a dose setting device that        is moved in a first direction away from a predetermined stop in        accordance with the size of a set dose and that moves back to        the predetermined stop during injection of the set dose, the        predetermined stop being configured for being fixedly arranged        relative to the housing,    -   an injection activator adapted to be activated to inject the set        dose,    -   a piston rod adapted to translate relative to the housing in a        distal direction in order to expel a set dose,    -   a rotatable driver coupled to the piston rod and including a        stored energy source configured to drive rotation of the driver        when the injection activator is activated to cause the piston        rod to translate relative to the housing,        Wherein:    -   the dose setting device defines a dose control member configured        for rotation around a first axis,    -   a first clutch arrangement arranged between the dose control        member and the driver, wherein the first clutch arrangement is        disengaged during dose setting so that the dose control member        rotates independently of the driver, and wherein the first        clutch arrangement engages upon activation of the injection        activator to enable the driver to rotate the dose control member        while causing the dose setting device to move back towards the        predetermined stop, and    -   a second clutch arrangement arranged between the driver and the        housing, wherein the second clutch arrangement is engaged during        dose setting so that the driver is prevented from rotating        during dose setting, and wherein the second clutch arrangement        disengages upon activation of the injection activator to enable        the driver to rotate relative to the housing.

In accordance herewith, an improved injection device is provided whichdue to the configuration of the first and the second clutch arrangementsoffers increased flexibility in the structural design of the device,ultimately allowing a more compact device to be provided. In addition,the design enables the dose setting arrangement to include a dosesetting device that moves relative to the housing of the device bothduring dose setting as well as during injection of a set dose. Inaccordance herewith, the dose setting device may include a doseindicator that may be viewed through a window either formed in thehousing or otherwise associated with the housing at a location that isrotationally fixed relative to the housing.

The dose setting device will typically be provided as a component thatdefines a minimum dose setting and a maximum dose setting and wherein acurrent position of the dose setting device between the minimum dosesetting and the maximum dose setting, when the injection device isshifted from a dose setting mode to a dose expelling mode, defines theamount that is expelled during expelling of a set dose. The dose settingarrangement may be so configured that doses can be dialled up anddialled down so that an initially set dose can be dialled down withoutcausing drug to be expelled from the device.

The dose setting device of the dose setting arrangement may in someembodiments comprise or be provided as a component that rotates relativeto the housing, such component being formed as a cylindrical member oralternatively a disc shaped member. A disc shaped member may be arrangedas a rigid member or otherwise as a flexible member such as a membermade of foil. In still other embodiments, the dose setting device is acomponent that is displaced linearly without rotation. In some forms thecomponent is formed as a mechanical dial having a series of dose indiciaformed along the length of travel of the component. For a cylindricalmember, such member may include a thread that engages a threadassociated or formed in the housing and wherein a series of dose indiciais formed along a helical path arranged in accordance with the lead ofthe thread. Alternatively to forming the dose setting device as a dial,a dial may be provided as a device that is separate from the dosesetting device.

In particular forms, the dose setting device rotates in unison with therotational movements of the dose control member, optionally allowing forrelative axial movements (i.e. movements parallel to the first axis)between the two components. In other embodiments, a gearing is providedbetween the rotational movements of the dose control member and the dosesetting device. In still other embodiments, the dose setting device isformed by the dose control member itself.

Typically, the drug cartridge for use with the injection device may beprovided in the form of a cylindrical cartridge having a piston movablein a distal direction towards an expelling end of the cartridge, wherethe expelling end of the cartridge is sealed by a penetrable septumadapted to be pierced by a subcutaneous injection needle.

In some embodiments of the injection device the driver defines a drivemember arranged for rotation coaxially with the dose control member. Insuch configuration, the drive member may be provided with a first trackdisposed thereon while the dose control member may be provided with asecond track. An end of content track follower is arranged between thedrive member and the dose control member where the end of content trackfollower is in engagement both with the first track and the second trackto follow each of the tracks. The first track and the second track areconfigured to cause the end of content track follower to move along thefirst axis when the dose control member is rotated relative to the drivemember. The end of content track follower moves towards an end ofcontent stop as the dose setting device is dialled up, the end ofcontent stop being arranged at a predefined position to prevent the dosesetting device from being rotated beyond a dose setting corresponding tothe end of track follower engaging the end of content stop.

Hence, an end of content feature may be provided to prevent a user fromdialling up a dose of a size exceeding the useable content of drugremaining in the cartridge. The end of content stop may be associatedwith the first track or the second track, for example by forming an endstop at the end of the respective track, i.e. on the drive member or thedose control member. At least one of the first and the second tracksforms a thread wherein the end of content stop is arranged fixedlyrelative to the at least one thread. The end of content stop may beprovided as a rotational stop to ensure a well-defined stop limitationposition.

The first clutch arrangement may be so configured that during doseinjection the first clutch arrangement prevents the drive member fromrotating relative to the dose control member. Hence, during injection,the end of track follower will maintain its position relative theengaging tracks and hence also relative to the end of content stop.

In some embodiments one of the first and the second tracks forms athread whereas the other one of the first and the second track forms anaxial track. In other embodiments both the first and the second tracksforms threads and wherein the lead of the first track is different thanthe lead of the second track. Hence, the end of content track followerwill be forced to move in an axial direction as the dose control membermoves relative to the drive member during dose setting.

The dose control member may be axially moveable back and forth relativeto the housing, e.g. between a default or inactivated proximal positionand an activated distal position. The dose control member may be biasedtowards the inactivated position by a spring element. In someembodiments the dose control member defines an injection activator whichmay form an injection button. In some embodiments, the dose controlmember is moved from the inactivated position and into an activatedposition responsive to an injection button being operated to inject theset dose. The injection button may be connected to the dose controlmember so that these two components are fixed relative to each otherwith respect to axial movements. The injection button and the dosecontrol member may be arranged to allow relative rotational movements.

In particular embodiments, the expelling of a set dose may be halted atany time by releasing finger pressure exerted on the injection button.When pressure is released the dose control member is automatically movedinto its proximal position due to the bias provided by spring element.Hence, in such situation, the second clutch arrangement re-engages whichthus prevents the drive member from rotating. However, expelling of theremaining part of the set dose may be continued by renewed pressing downthe injection button.

In particular embodiments, the dose control member operates the firstclutch arrangement and the second clutch arrangement. When the dosecontrol member is in the inactivated position the first clutcharrangement disengages the coupling between the dose control member andthe driver while the second clutch arrangement locks the driver againstrotational movement relative to the housing. When the dose controlmember is in the activated position the first clutch arrangement couplesrotational movement between the dose control member and the driver whilethe second clutch arrangement unlocks the driver with respect torotational movements relative to the housing.

In some forms the injection device comprises a dose setting membercoupled to the dose setting device for operating the dose settingdevice, e.g. so that the dose setting device rotates as the dose settingmember rotates. The dose control member may interconnect the dosesetting member and the dose setting device.

The dose setting member may be configured to be manually gripped by thehand of the user for dialling up and dialling down the dose to beinjected. In other forms, a separate dosage selector is coupled to thedose setting member so that the dose setting member is rotated as thedosage selector is manipulated by the hand of the user. In such forms,the dosage selector may be provided as an endless band that is coupledto the dose setting member so that movement of flexible band istransformed into a rotation of the dose setting member.

A third clutch arrangement may be arranged between the dose controlmember and the dose setting member, wherein the third clutch arrangementis engaged during dose setting so that the dose control member rotatestogether with the dose setting member, and wherein the third clutcharrangement disengages upon activation of the injection activator toenable the dose control member to rotate independently from the dosesetting member.

Also, a fourth clutch arrangement may be provided which controls therotation of the dose setting member relative to the housing so that whenthe injection activator is in the inactivated position the rotation ofthe dose setting member is enabled whereas when the injection activatoris in the activated position rotation of the dose setting member isprevented.

The dose control member may in some embodiments be configured to operateeither one or both of the third and fourth clutch arrangements, i.e. incorrespondence with the axial position of the dose control member.Hence, in particular embodiments the dose control member may control thefirst, the second, the third and the fourth clutch arrangements. Inaccordance herewith, safe control of the device is provided with a largedegree of control of the components of the device during dose settingmode as well as during dose expelling mode.

As noted above, the dose control member is configured for rotationaround a first axis. In some embodiments, the piston rod extends alongthe first axis which enables the general form factor of the injectiondevice to be formed with a cylindrical form factor. In otherembodiments, at least the piston engaging end of the piston rod and thecylindrical cartridge may be configured to extend along a second axisthat is different than the first axis. The second axis may be arrangedin parallel with the first axis but may be offset by a certain distance.The driver may in such situations comprise a drive nut that rotatesaround the second axis and that couples with the piston rod so that thepiston rod is moved along the second axis as the drive nut is rotated.

The piston rod may be formed as a flexible piston rod having a first endextending along the second axis and adapted to engage a piston of a heldcartridge and wherein the second end of the piston rod is adapted to beflexed away from the second axis. The flexible piston rod may beprovided as a series of interconnected links or alternatively as anincompressible helical spring. In still other embodiments, the pistonrod is formed by a rigid rod shaped member.

As commonly known for injection devices, the piston rod may include oneor more threads or alternatively a single axially extending track incombination with a single thread, where each track or thread is engagingrespective corresponding geometries in the drive nut and a guide memberfixedly arranged relative to the drug cartridge.

The stored energy source may comprise energy sufficient to drive thepiston rod for expelling the entire useable contents of drug containedin the cartridge. The stored energy source may be provided as a springdevice wherein the spring device may be tensed already duringmanufacture so that the user is not required to provide energy to thespring device prior to activation of the injection activator forexpelling a set dose. The spring device may for example be provided as aconstant force spring. In particular embodiments, the spring device isprovided as a constant force spring having a first end that is wouldaround an axis a) and a second end that is wound around another axis b)that is offset relative to said axis a) by a certain distance.

Examples of spring devices include an s-shaped constant force spring.Such spring device may be arranged in an s-shaped configuration wherethe first end is wound around the axis of the dose control member andthe second end is wound around the axis of the cartridge.

The housing of the medical device may be so shaped and sized as to allowit to be held in a hand of the user and easily carried in a pocket.

Thus, in a second aspect of the invention an injection device forsetting and injecting set doses from a held drug cartridge is provided.The injection device comprises:

-   -   a housing defining proximal and distal ends,    -   a dose setting arrangement including a dose setting device that        is moved in a first direction away from a predetermined stop in        accordance with the size of a set dose and that moves back to        the predetermined stop during injection of the set dose, the        predetermined stop being configured for being fixedly arranged        relative to the housing,    -   a piston rod adapted to translate relative to the housing, in a        distal direction in order to expel a set dose,    -   a driver coupled to the piston rod, the driver being adapted to        rotate during dose injection to cause the piston rod to        translate relative to the housing, and    -   a mechanism adapted for coupling rotational movement of the dose        setting device with rotational movement of the driver such that        the driver exclusively rotates when the dose setting device        moves back towards the predetermined stop during injection of        the set dose, The injection device further defines:    -   a first component that rotates around a second axis as the        driver rotates during injection but remains rotationally fixed        relative to the housing during dose setting, the first component        having a first track disposed thereon,    -   a second component that is arranged coaxially with the first        component for rotation around the second axis, wherein the        second component rotates as the dose setting device rotates        during dose setting and wherein the second component is        rotatably fixed relative to the housing during dose injection,        the second component having a second track disposed thereon, and    -   a secondary stop track follower arranged between the first        component and the second component, the secondary stop track        follower being in engagement with the first track and in        engagement with the second track, wherein the first track and        the second track are configured to cause the secondary stop        track follower to move along the second axis when the first        component and the second component rotate relative to each        other, and wherein, if the predetermined stop fails to stop the        driver at the end of injection, the secondary stop track        follower moves towards a safety stop to prevent the driver from        rotating further.

In accordance herewith, an improved injection device with a secondarysafety stop is provided which provides an increase in safety ofoperation. In case the primary limitation function associated with thedose setting device fails, or in case a clutch arrangement within thedevice fails, the secondary stop function will prevent the injectiondevice from running loose.

Compared to prior art injection devices, the invention provides a fasterresponding safety system that will be better synchronized with thepredetermined stop associated with the dose setting device that isintended to limit dose movements at the end of the dose expellingmovement. Further the invention provides for increased flexibility fordesigning the safety system due to the fact that the secondary safetystop mechanism may be positioned at a location where it does not take upspace required by other components.

In particular where the secondary safety stop is coupled to a componentother than the piston rod, i.e. where the secondary stop track followerdoes not engage the piston rod, the lead of the one more threads of thesecondary safety stop may differ from the lead of the piston rodproviding increased opportunities for designing the secondary stopfunction with superior operability.

In some embodiments one of the first track and the second track isshaped to form a thread whereas the other one of the first track and thesecond track forms an axial track.

In other embodiments both the first track and second track form threadswherein the lead of the first track is different than the lead of thesecond track.

At least one of the first track and the second track forms a threadwherein the safety stop is arranged fixedly relative to the at least onethread.

In accordance with the first aspect, the first component is a componentseparate from the piston rod. In some embodiments the driver defines thefirst component.

The safety stop may be provided as a rotational stop surface adapted toabut a rotational stop surface provided on the secondary stop trackfollower to prevent further rotation of the first component beyond thesafety stop.

In different further embodiments, the various features according to thefirst aspect are combined with one or more features according to thesecond aspect.

As used herein, the term “drug” is meant to encompass anydrug-containing flowable medicine capable of being passed through adelivery means such as a hollow needle in a controlled manner, such as aliquid, solution, gel or fine suspension. Further, “drug” is meant alsoto encompass mediums for nasal or pulmonary administration.Representative drugs include pharmaceuticals such as peptides, proteins,and hormones, biologically derived or active agents, hormonal and genebased agents, nutritional formulas and other substances in both solid(dispensed) or liquid form. In the description of the exemplaryembodiments reference will be made to the use of insulin.Correspondingly, the terms “subcutaneous” and “transcutaneous” injectionor infusion is meant to encompass any method of transcutaneous deliveryto a subject.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following the invention will be further described with referencesto the drawings, wherein

FIG. 1 shows a cross sectional side view of an embodiment of a medicalinjection device 1 in accordance with the invention,

FIG. 2 shows an exploded perspective view of the main components of theinjection device 1 of FIG. 1,

FIG. 3 shows an exploded sectional view of the main components of theinjection device 1 of FIG. 1,

FIG. 4a is a cross sectional side view of the device of FIG. 1 in aninitial state before the setting of a dose,

FIG. 4b is a cross sectional side view of the device of FIG. 1 where adosage selector 200 has been operated to set a particular size of adose,

FIG. 4c is a cross sectional side view of the device of FIG. 1 where aninjection button 300 has been pushed down and where the injection of theset dose has been completed,

FIG. 4d is a cross sectional side view of the device of FIG. 1 after thecompletion of the injection of the set dose and wherein the injectionbutton has been released,

FIG. 5a , shows a cross sectional side view of components relating tothe drive mechanism of the device shown in FIG. 1,

FIG. 5b is a perspective proximal view of the components shown in FIG. 5a,

FIG. 6 is a perspective proximal view of a dose setting member 250 ofthe device shown in FIG. 1,

FIGS. 7a, 7b and 7c depict detailed perspective views of components 700,270 and 950 relating to a secondary stop limiter,

FIG. 8 shows a perspective cross sectional view of the components ofFIGS. 7a, 7b and 7c in an assembled state,

FIG. 9 shows a perspective cross sectional partial view of componentsshown in FIG. 5 b,

FIG. 10 is a perspective distal view of selected components of FIG. 5 b,

FIG. 11 is a perspective proximal view of selected components relatingto the dose setting and driving mechanism of the injection device 1 ofFIG. 1, and

FIG. 12 is a schematic representation of the drive spring of theinjection device 1 of FIG. 1.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

The shown figures are schematic representations for which reason theconfiguration of the different structures as well as the relativedimensions are intended to serve illustrative purposes only.

In the context of the following discussion it may be convenient todefine that the term “distal end” in the appended figures is meant torefer to the end of the injection device which usually carries theinjection needle whereas the term “proximal end” is meant to refer tothe opposite end pointing away from the injection needle, i.e. the endcarrying an injection button as depicted in FIG. 1. The term “axial”refers to directions parallel with a central longitudinal axis of a heldcylindrical drug cartridge.

FIG. 1 shows a cross sectional side view of an embodiment of aninjection device 1 for use by a patient for medical self-treatment, theinjection device 1 being configured for repetitively setting andinjecting individually set doses of a drug. The injection device 1includes a housing (110,120,130,140) which along a main axis defines anelongated structure and which at least along a part of its length, in adirection transverse to the main axis, is formed with a non-cylindricalcross section exhibiting a somewhat flat shape, such a device beinggenerally referred to as a “closer” device.

The injection device 1 is shown as a cartridge-based injection devicewherein a drug filled cartridge 10 is accommodated within the housing(110,120,130,140). The cartridge 10 has an elongated body 11 and apierceable septum 12 covering a distal outlet end of the body 11 forcooperation with a replaceable subcutaneous injection needle (notshown). Also, cartridge 10 includes a piston 13 mounted within body 11for sliding movement along an expelling axis of the cartridge. In FIG. 1the expelling axis lies in the plane of the cross section. When a needleassembly (not shown) is mounted on the cartridge 10, piston 13 may beforced in the distal direction along the expelling axis for expellingportions of the drug accommodated in the cartridge. Either the cartridge10 or the housing (110,120,130,140) defines a needle mount adapted toreleasably mount a needle assembly, e.g. a double pointed injectionneedle. The injection device 1 shown in FIG. 1 may further include a cap(not shown) which detachably mounts relative to the distal end ofhousing 110 for protection of the contents of the cartridge 10 andoptionally for protecting an injection needle which may be mounted atthe distal end of the device.

Referring to FIG. 1, the main components of the injection device 1 willnow be described. FIG. 1 only includes references referring to the maincomponents. Also exploded perspective and cross-sectional views of themain components of the injection device 1 are depicted on FIGS. 2 and 3.For further details to each of the components reference is made to theremaining figures, in particular FIGS. 4a -4 d.

The housing (110,120,130,140) comprises a distal housing part 110, anintermediary housing part 120, a proximal housing part 130 and acartridge housing part 140. Injection device 1 further comprises a doseinjection mechanism operable by an injection activator in the form of aninjection button 300 and a dose setting mechanism operable by a dosageselector 200.

The dose injection mechanism comprises a piston rod 800 that engages thepiston 13 (by means of a piston washer). Piston rod 800 extends axiallyin the proximal direction away from piston 13. In the shown embodiment,the piston rod 800 is of a flexible type having a piston engaging endand a free end and wherein the flexibility is provided by forming thepiston rod as a series of interconnected links. The flexibility allowsthe free end of the piston rod to be deflected away from the expellingaxis. It is to be noted that FIG. 1 and FIGS. 4a-4d only show the mostdistal part of piston rod 800, the remaining parts of piston rod 800 isfor clarity reasons omitted from these drawings. However, the structureof piston rod 800 is more clearly depicted in FIGS. 2 and 3 where it canbe seen that, in the depicted operating state for the piston rod 800,the piston engaging end of the piston rod 800 assumes a straight portionwhereas the free end assumes a bended portion.

In the shown embodiment, the piston rod 800 is a segmented type rod thatconsists of interconnected hinged rod elements that are adapted toswivel relative to each other at least in a particular direction ofrotation so that the free end of the piston rod 800 may bend away fromthe expelling axis. When parts of the piston rod 800 assume a straightconfiguration, the rod elements are substantially incompressible so thatthe piston rod 800 is able to act as a push rod. Along its longitudinalextension piston rod 800 defines a first track and a second track eachadapted to cooperate with a respective one of a nut member and arotation control member so that relative rotation between the nut memberand the rotational control member results in a longitudinal movement ofpiston rod 800. In alternative embodiments, the piston rod may be formedas a coiled axially incompressible spring which along its length isdeflected away from its neutral rectilinear shape and that serves totransfer forces to the piston of the cartridge.

In the shown embodiment, the first track of the piston rod 800 definesan external thread (not referenced) and the second track (notreferenced) defines a rotation control geometry that cooperates with aguide member 112 formed in distal housing part 110 to ensure that atleast the straight portion of piston rod 800 is kept substantiallyin-rotatable. The rotation control geometry of the piston rod 800 mayfor example include one or more planar portions adapted to mate with acooperating structure of the guide member 112 so as to prevent rotationbetween the piston rod 800 and the cooperating guide member 112.

As shown in FIG. 1, the dose injection mechanism of injection device 1comprises a drive nut 700 having an internal thread 709 that engages theexternal thread of the piston rod 800. Drive nut 700 is mountedrotatably free but axially fixed relative to the housing so that drivenut 700 is able to rotate around the expelling axis, the amount ofrotation of drive nut 700 thereby being decisive for the axial distaldisplacement of the straight portion of the piston engaging end of thepiston rod 800.

In an alternative configuration of device 1 the drive nut would includea geometry which engages an axially extending track of the piston rodwhereas the guide member would be threadedly engaged with a thread ofthe piston rod. A still further alternative is to use a piston rod withtwo separate threads having different thread leads where each respectivethread is engaging a corresponding thread in the piston nut and theguide member. It is to be noted that in the context of the presentapplication the term “drive nut” is means to cover all these variants ofa drive nut.

The dose injection mechanism further includes a drive member 500 that ismounted rotatable but axially fixed relative to the housing, the drivemember 500 being in rotational engagement with drive nut 700 so that thedrive nut 700 rotates as the drive member 500 rotates. An actuatorproviding a stored energy source exerts a substantially constant drivingforce on drive member 500 in the particular direction of rotation thatenables the piston rod 800 to be driven in the distal direction. In theshown embodiment, the stored energy source comprises a drive spring 560in the form of a flat spiral spring that initially is stored on astorage drum 600 and which spools onto the drive member 500 as theenergy accumulated in the drive spring 560 is released for driving thepiston rod 800 in the distal direction. As regards further details ofthe drive mechanism reference is made to the discussion further below inrelation to FIGS. 10 and 11.

As noted above, injection device 1 further includes a dose settingmechanism allowing a user to set a desired dose to be injected by meansof the dose injection mechanism.

Coupled to the dose setting mechanism and the dose injection mechanismis a clutch mechanism that ensures that during dose setting, no movementof the drive mechanism is possible and that ensures that during doseinjection the dose setting cannot be manipulated to alter a dose settingthat has previously been set. Hence the clutch mechanism defines theinjection device 1 to be operated in a dose setting mode and in a doseexpelling mode. In the shown embodiment the clutch mechanism includes 4separate clutch arrangement mechanisms. In FIGS. 4a-4d and in thefollowing discussion these four clutch arrangement mechanisms arerespectively designated a first, a second, a third and a fourth clutcharrangement (C1, C2, C3, C4).

The injection button 300 is arranged to protrude in a proximal directionfrom the proximal housing part 130 and arranged for limited axialmovement between a default proximal position and a distal pressed downposition. The mode of the clutch mechanism is controlled by theinjection button 300. When the injection button 300 is depressed intothe distal position the injection device 1 is in dose expelling modewhereas when the injection button 300 assumes its default proximalposition the injection device 1 is in dose setting mode. The injectionbutton 300 is arranged relative to the housing of the device 1 so thatthe injection button 300 cannot rotate.

The clutch mechanism includes a drive clutch 370 mounted between thedrive member 500 and the housing part 120 that controls whether or notdrive member 500 is allowed to rotate relative to the housing. Theclutch mechanism will be described in greater detail further below.

The dose setting mechanism comprises a dose setting member 250 that ismanually operable by turning dosage selector 200. Dose setting member250 is axially fixed relative to the housing but rotates around an axisdefining a dose setting axis that extends in parallel with the expellingaxis but is separated from the expelling axis by a certain distance. Adosage selector connector 230 couples movement of dosage selector 200with rotation of the dose setting member 250 so that the dose settingmember 250 may be rotated in either direction controlled by movement ofthe dosage selector 200. Between dosage selector connector 230 and dosesetting member 250, a slip coupling may be arranged to preventdestruction on the mechanism in case excessive forces are being appliedon dosage selector 200. In the shown embodiment, and as more clearlyindicated on FIG. 2, dosage selector 200 is arranged along a crosssection transverse to the expelling axis that runs through the housingi.e. between intermediary housing part 120 and proximal housing part130. Dosage selector is formed as an endless flexible band 200 thatgenerally conforms to the shape of the exterior surfaces of housingparts 120 and 130 due to the engagement with guiding structures formedin housing parts 120 and 130. Hence, the flexible band 200 may be movedalong the directions of circumference of the flexible band in a firstdirection to increase the setting of a dose and in the oppositedirection for decreasing an already set dose. An interior surface of theflexible band 200 forms a series of teeth that cooperate with dosageselector connector 230 to transform movement of flexible band 200 into arotation of dose setting member 250. In other embodiments, instead of aflexible band 200 the dosage selector may be provided as a wheel or knobthat may be manually turned for operating the dose setting mechanism.The dosage selector may for example be formed by dose setting member 250by arranging openings in the housing of the device suitable formed toallow manual manipulation of dose setting member 250.

Further, a dose control member 350 extends longitudinally along the dosesetting axis. The dose control member 350 is arranged in the housing forlimited axial movements between a proximal position and a distalposition. A pin 310 of injection button 300 extends distally frominjection button 300 along the dose setting axis and into an opening ofdose control member 350. Pin 310 serves to couple axial movements of theinjection button 300 with axial movements of dose control member 350 butallows the dose control member 350 to be rotated around the dose settingaxis.

A compression spring 360 is arranged in the housing to exert aproximally directed force on the dose control member 350 to bias thedose control member 350 and hence the injection button 300 into theproximal (default) position.

Positioned coaxially with the dose control member 350 and in distalhousing part 110 is a dose dial scale 400 arranged. In the shownembodiment, the dose dial scale 400 is provided as a tubular sleeve thatdefines an exterior thread 407 engaging an interior thread 117 formed indistal housing part 110 (see FIG. 4a ). Along an exterior helical path,the dose dial scale 400 is provided with a series of numerals eachreferring to individually selectable doses of a drug that the injectiondevice 1 is designed to set and to expel. Housing part 110 is providedwith an opening or window (not shown) through which a current dosesetting is viewable.

Dose dial scale 400 is adapted to rotate together with the dose controlmember 350 but dose dial scale 400 is movable in axial directionsrelative to dose control member 350. In the shown embodiment thisfunction is facilitated by means of an interior surface of the dose dialscale 400 that defines one or more axially extending tracks 401 thatcooperates with corresponding one or more axially extending tracks 351formed on an exterior surface of the dose control member 350 (see FIGS.4a and 11).

Dose dial scale 400 includes a minimum limiting stop surface and amaximum limiting stop surface that define two extreme end positions thatdose dial scale may assume during operation of the injection device 1preventing operation outside the two extreme end positions. As bestviewed in FIG. 3, dose dial scale 400 includes said two stop surfaces asaxially extending ledges (non-referenced) that each is adapted tocooperate with a respective dose stop surface defined by distal housingpart 110 and intermediary housing part 120. In the shown embodiment,dose dial scale 400 is adapted to experience a total rotation of 3.5turns relative to the housing between a zero dose position and a maximumdose position. In the shown embodiment the dose dial scale 400 isprovided with 100 separate dose markings along a helical path.

Dose control member 350 serves several functions relating both to thedose setting mechanism and to the dose injection mechanism of injectiondevice 1.

When the injection device 1 is in dose setting mode, i.e. when theinjection button 300 is in the default proximal position, dose controlmember 350 couples a rotation of the dose setting member 250 withrotation of the dose dial scale 400.

When the injection device 1 is in dose expelling mode, i.e. when theinjection button 300 is in the pushed down position, the dose controlmember 350 couples rotation of the drive member 500 with rotation of thedose dial scale 400.

Dose control member 350 further includes a resilient tooth 359 (see FIG.4a ) adapted to engage a series of axial splines 119 formed in thedistal housing part 110. The resilient tooth 359 and the splinesperforms as a click mechanism that makes the dose setting occur indiscrete steps, e.g. corresponding to the number of numerals provided onthe dose dial scale 400. During dose setting, the injection device 1hereby emits a series of clicks as the dosage selector 200 ismanipulated. In addition, as a dose of drug is being expelled, the clickmechanism emits a series of click sounds as the dose control member 350is rotated, e.g. one click as each unit of doses being expelled. Due tothe axial splines 119, the dose control member 350 is allowed to moveaxially without this having influence on the performance on the clickmechanism.

Besides the above functions, also the function of the drive clutch 370is coupled with movements of the dose control member 350. In addition anend of content mechanism (EOC) including an EOC track follower 900 iscoupled to the movement of dose control member 350. As will beappreciated by a person skilled in the art, an end of content mechanismis a mechanism which prevents the setting of a dosage amount whichexceeds the useable dose amount remaining in the drug cartridge, i.e.the amount remaining in the cartridge that can be expelled with therequired accuracy.

The function of the drive clutch 370 is provided by means of a secondclutch arrangement C2 (122, 372) between the drive member 500 and theintermediary housing part 120. Drive member 500 and drive clutch 370 arerotationally locked relative to each other so that they rotate togetherbut drive clutch 370 may be moved slightly in the axial directionrelative to the drive member 500. Between drive clutch 370 and dosecontrol member 350 is a coupling which ensures that the axial movementsof drive clutch 370 follows axial movements of the dose control member350 but relative rotational movements between these two components areenabled. Drive clutch 370 includes a series of teeth 372 adapted toengage corresponding teeth 122 formed in the intermediary housing part120 (see FIGS. 4a, 4c and 11). Hence, when the injection button is inthe proximal position, the drive member 500 is locked relative to thehousing so that rotation of drive member 500 is prevented. Upondepression of injection button 300, the drive member 500 is releasedfrom the rotational locking relative to the housing allowing the drivemember 500 to rotate. Hence, only when the injection button is depressedthe drive member 500 is allowed to rotate and an expelling operation mayin this way be facilitated.

A first clutch arrangement C1 (502, 352) is provided between the drivemember 500 and the dose control member 350. The drive member 500 definesa distal circular opening along which a series of teeth 502 are arranged(see FIGS. 4a and 10). The dose control member 350 includes a series ofcorresponding teeth 352. When the dose control member 350 is in itsdistal position (see FIGS. 4a and 10), the teeth 352 of dose controlmember 350 engage with the teeth 502 of drive member 500 to effectivelylock the two components against relative rotation. Hence when theinjection button 300 is pushed down during dose injection, the rotationof the drive member 500 is coupled with rotation of dose control member350. When the dose control member 350 is moved into its proximalposition, the teeth 352 are moved out of engagement with the teeth 502of drive member 500. Hence when the injection button 300 is released,rotation of the dose control member 350 relative to drive member 500 isenabled.

A third clutch arrangement C3 (253, 353) is provided between the dosesetting member 250 and the dose control member 350. The proximal part ofdose control member 350 includes a series of teeth 353 (see FIG. 4a andFIG. 11) that is adapted to engage corresponding teeth 253 formed indose setting member 250 (see FIGS. 4a, 5a and 6). When the dose controlmember 350 is in its proximal position, the teeth 353 are adapted toslide into engagement with the teeth 253 of dose setting member 250.Hence, when the injection button 300 is in its released position, therotation of dose setting member 250 during dose setting is coupled withrotation of the dose control member 350. When the dose control member350 is in its distal position, the teeth 352 are moved out of engagementwith the teeth 502 of drive member 500. Hence when the injection button300 is pushed down, rotation of the dose control member 350 relative todose setting member 250 is enabled.

A fourth clutch arrangement C4 (254, 314) is provided between the dosesetting member 250 and the injection button 300. Dose setting member 250defines a proximal circular opening along which a series of teeth 254are arranged (see FIGS. 4a, 5a and 6). The distally extending pin 310 ofinjection button 300 includes a series of corresponding teeth 314 (seeFIGS. 4a and 3). When the dose control member 350 is in its distalposition (shown in FIG. 4c ), the teeth 314 of injection button 300engage with the teeth 254 of the dose setting member 250 to preventrelative rotation between the dose control member 350 and injectionbutton 300. Hence, when the injection button 300 is pushed down duringdose injection, rotation of the dose setting member 250 relative to thehousing is prevented. In the disclosed embodiment the dosage selector200 cannot be operated during dose injection. When the dose controlmember 350 is moved into its proximal position (shown in FIGS. 4a, 4band 4d ), the teeth 314 are moved out of engagement with the teeth 254of the dose setting member 250. Hence, when the injection button 300 isreleased, rotation of the dose setting member 250 relative to thehousing is enabled which allows for a dose to be set by operating dosageselector 200.

As shown in FIGS. 4a, 5a and 5b the drive member 500 includes acylindrical section forming a gear wheel 505. Also the drive nut 700includes a cylindrical section forming a gear wheel 705 that engagesgear wheel 505. Hence a rotation of drive member 500 in a particulardirection during dose injection is transferred to rotation in theopposite direction of drive nut 700.

FIGS. 10 and 11 show perspective representations of selected componentsof the drive mechanism included in injection device 1.

The drive member 500 includes a further cylindrical spring receivingsection 550 that is arranged to reside next to the storage drum 600 inthe same axial position in the housing of the device as the storage drum600. Drive nut 700 provides a bearing surface adapted to receive storagedrum 600 so that storage drum may rotate independently relative to thedrive nut 700. In this embodiment, the drive spring 560 is provided as aconstant force spring arranged between the storage drum 600 and thecylindrical spring receiving section 550 of drive member 500. The spring560 may be arranged to constitute an S-shaped curve in a mannerschematically shown on FIG. 12. The drive spring 560 may be adapted tohave a natural tendency to reside on the storage drum 600. However,during production of the injection device 1 the drive spring 560 isforced onto the cylindrical spring receiving section 550 therebyaccumulating energy in drive spring 560. Upon release, the accumulatedenergy of the drive spring 560 urges drive member 500 to rotate whilethe drive spring 560 gradually winds up onto storage drum 600. Thecylindrical spring receiving section 550 includes means (non-referenced)to fasten the end of the drive spring 560 so that slippage between thedrive spring 560 and drive member 500 will not occur.

In other embodiments, the direction of movement may be reversed so thatthe drive spring 560 may gradually seek to move onto the drive member500 during energy release, i.e. during dose expelling. Also otherconfigurations of drive springs than the shown S-type spring may beused.

In the shown embodiment, the drive spring 560 is fully loaded during theassembly of the injection device 1. When purchased by the user, thedrive spring contains sufficient energy to deliver the entire useableamount of drug contained in the cartridge 10.

During dose setting, the dose control member 350 is rotated inaccordance with the dose set as adjusted by means of dosage selector200. This has the effect that the dose dial scale 400 is rotated awayfrom its zero dose position. The amount of rotation of dose dial scale400 therefore exactly corresponds to the selected dose size. During thismovement the first clutch arrangement C1 is in the released state sothat the drive member 500 is not being operated. It is noted that duringdose setting, the second clutch arrangement C2 is engaged meaning thatthe drive member 500 is prevented from rotating.

The dose setting may be performed by dialling up and down dosageselector 200 until a desired dose shows up in the dose window of thehousing. After the desired dose has been dialled, and after an injectionneedle has been mounted relative to the drug cartridge 10, the desireddose is ready for injection.

After applying a suitable force on the injection button 300 to pressdown the injection button to the distal position (see FIG. 4c ), thefirst clutch arrangement C1 is in the engaged state and the secondclutch arrangement C2 is in the released state. Hence, the drive member500 is released for rotation relative to the housing and is urged byspring drive 560 to rotate thereby carrying with it the dose controlmember 350. As long as the injection button 300 is maintained in thedepressed position, the drive member 500, the dose control member 350and the dose dial scale 400 rotates together towards the zero doseposition. All this time the drive nut 700 rotates to drive forward thepiston rod 800 resulting in the expelling of the drug through theattached needle. The movement is stopped when the minimum limiting stopsurface of the dose dial scale 400 engages the corresponding dose stopsurface formed in distal housing part 110. This simultaneously stops thedrive member 500 from rotating and the piston rod 800 will move nofurther.

It is to be noted that during dose injection procedure, the expellingmay be halted at any time by releasing the finger pressure exerted onthe injection button 300. When pressure is released the dose controlmember 350 is automatically moved into its proximal position due to thebias provided by compression spring 360, Hence, clutch arrangement C2re-engages which thus prevents the drive member 500 from rotating.However, expelling of the remaining part of the set dose may becontinued by renewed pressing down the injection button 300.

Hence the dose dial scale 400 acts as a metering device during dosesetting where the return movement of the dose dial scale 400 duringinjection determines the amount that will be expelled. In this way thedose dial scale provides a primary stop limiter.

The injection device 1 further includes a secondary stop limiter whichperforms as a safety back up function in case that a mechanical erroroccurs somewhere in the dose setting mechanism or somewhere in the doseinjection mechanism. In the shown embodiment, the drive nut 700 isassociated with such a secondary stop limiter. As apparent from FIG. 1and in particular FIGS. 5a-5b, 7a-7c , 8 and 9 the secondary stoplimiter includes the said drive nut 700, a secondary stop ring 270arranged coaxially with the drive nut 700 and a secondary stop trackfollower 950 arranged between the drive nut 700 and secondary stop ring270.

As shown in FIG. 7a , the drive nut 700 includes an external thread 707provided on a proximal cylindrical portion thereof. The drive nut 700defines a stop surface 708 located at a particular position relative tothe thread 707.

Referring to FIG. 7b , the secondary stop track follower 950 is in thisembodiment in the form of a cylindrical nut that defines an internalthread 957 adapted to engage the thread 707 of drive nut 700. Thesecondary track follower 950 defines a stop surface 958 that is adaptedto engage the stop surface 708 provided on drive nut 700 for aparticular relative rotational and axial position between the secondarystop track follower 950 and drive nut 700. The secondary stop trackfollower 950 further comprises one or more track elements 953 extendingradially outwards from an outer cylindrical surface of secondary stoptrack follower 950.

As shown in FIG. 7c , the secondary stop ring 270 is a generallycylindrical sleeve that includes a cylindrical bearing surface(non-referenced) adapted to be rotatably supported in the housing at afixed location thereof. An interior surface of the stop ring 270includes one or more axially extending tracks 273 each of which isadapted to cooperate with respective ones of track elements 953 of thesecondary stop track follower 950. In this way the secondary stop trackfollower 950 is configured to rotate with the secondary stop ring 270but allows relative axial displacement of secondary stop track follower950 relative to secondary stop ring 270. A cylindrical section ofsecondary stop ring 270 forms a gear wheel 275 that is adapted to engagethe gear wheel 255 section of dose setting member 250.

In the assembled state the drive nut 700, the secondary stop ring 270and the secondary stop track follower 950 forms an assembly that moreeasily is viewed in FIGS. 5a , 8 and 9.

Due to the threaded engagement between the secondary stop track follower950 and the drive nut 700, the secondary stop track follower 950 will bemoved back and forth in the axial direction as the secondary stop trackfollower 950 and the drive nut 700 rotate relative to each other.

Before the setting of a dose, when the dose dial scale 400 indicates thezero dose setting through the window in the housing, the secondary stoptrack follower 950 will assume an initial position relative to the drivenut 700. In this state the stop surface 958 of the secondary trackfollower 950 will be situated in close proximity with respect to thestop surface 708 provided on drive nut 700. As a dose is dialled up bymanipulating dosage selector 200 the dose setting member 250 will berotated and, due to the engagement between gear wheel 255 and gear wheel275, the secondary stop ring 270 and the secondary track follower 950will be rotated as well. As the drive nut 700 is maintainednon-rotatable during dose setting, due to the threaded connection 707and 957, the secondary track follower 950 will be moved in the proximaldirection so that the stop surface 958 of the secondary track follower950 will be moved further away from the stop surface 708 provided ondrive nut 700.

During dose injection, when the injection button 300 is pressed down,the dose setting member 250 is prevented from rotating and hence thesecondary stop ring 270 and the secondary track follower 950 areprevented from rotating as well. However, as the drive nut 700 rotatesduring injection, due to the threaded connection 707 and 957, thesecondary track follower 950 will be moved in the distal direction.

In a correctly working injection device 1, upon reaching the end of dosestate where the dose dial scale 400 is located so that its minimumlimiting surface engages the corresponding dose stop surface defined bythe distal housing part 110 (corresponding to the zero dose position),the secondary track follower 950 will be moved to assume the initialposition as referred to above. In this position the stop surface 958 ofthe secondary track follower 950 will again be situated in closeproximity with respect to the stop surface 708 provided on drive nut700.

In case a mechanical failure occurs in the injection device, such as afailing primary stop limiter, a failing first clutch arrangement C1 or afailing second clutch arrangement C2, the biasing force exerted by thedrive spring 560 on drive member 500 may cause the drive member to runfreely causing the drive nut 700 to rotate and the piston rod 800 tomove in the distal direction in an uncontrolled manner. However shouldsuch a situation arise, the drive nut 700 may slightly rotate but soonthe secondary stop limiter will prevent further rotation of drive nut700 as the stop surface 958 of the secondary track follower 950 will bein abutment with the stop surface 708 provided on drive nut 700.

In the shown embodiment, the drive nut 700 defines a thread 707 whereasthe stop ring 270 defines one or more axially extending tracks 273 wherethe thread 707 and the tracks 273 engage corresponding structures on thesecondary track follower 950. A similar function may be obtained byrearranging the thread to be disposed on the stop ring 270 and theaxially extending tracks to be disposed on the drive nut 700 andrearranging the structures on the secondary track follower 950accordingly. In still other embodiments, the secondary track follower950 defines two threaded sections where each of the threaded sectionsoperate with corresponding threads formed on the drive nut 700 and thestop ring 270 respectively. In such embodiment, the two threadedengagements are provided with threads of different lead so that thesecondary track follower 950 is forced to move axially as the drive nut700 and the stop ring 270 rotate relative to each other.

In the shown embodiment, the secondary track follower 950 is formed as acylindrical nut. In alternative embodiments, the secondary trackfollower 950 may alternatively be provided as a half-nut or forminganother structure such as ball clamped between tracks formed in thedrive nut 700 and the stop ring 270 where the tracks have differentlead.

The above mentioned end of content (EOC) mechanism will now be morefully described referring generally to FIG. 4a . In the shownembodiment, the dose control member 350 includes one or morelongitudinal extending ribs 354 provided along an exterior cylindricalsurface thereof. The drive member 500 includes an interior cylindricalsurface that defines an interior thread 507. And end of content trackfollower (EOC track follower) 900 is formed as a cylindrical nut andarranged coaxially with the drive member 500 and the dose control member350 so that the EOC track follower is located between the drive member500 and the dose control member 350. The EOC track follower 900 definesan external thread 907 that cooperates with internal thread 507 of drivemember 500. EOC track follower 900 further defines one or more internalaxial recesses each adapted to cooperate with the one or morelongitudinal extending ribs 354 of dose control member 350.

A not shown EOC limitation stop is associated with a proximal part ofthe thread 507 of drive member 500. In a known manner such stop maydefine a rotational stop surface adapted to engage a rotational stopsurface (not shown) of the EOC track follower 900 for a particularrelative axial and rotational position between the EOC track follower900 and the drive member 500. The said EOC limitation stop limits themovement of the EOC track follower 900 in the proximal direction so thatthe settable size of the dose is limited to dosage amounts to which acorresponding dosage remains in the cartridge 10. In this way the dosageselector 200 cannot dial up a dose that is larger than the remaininguseable dose accommodated in the cartridge.

Prior to use of the injection device, where the cartridge 10 is full andthe piston rod 800 is located in the position shown on FIG. 4a , the EOCtrack follower 900 is positioned in an initial axial position relativeto the housing (see FIG. 4a ). During dialling up a dose the EOC trackfollower 900 is rotated as the dose control member 350 rotates relativeto the drive member 500. Due to the threaded engagement 507, 907, theEOC track follower is moved in the proximal direction as a dose isdialled up (see FIG. 4b ). Should the dosage selector 200 be moved fordialling down a previously set dose, the EOC track follower 900 willmove in the distal direction in accordance with the reduction in dosesize.

When an injection is initiated, the dose control member 350 will move toits distal position. This has no influence on the axial position of theEOC track follower 900. During injection wherein the first clutcharrangement C1 is in the engaged state, the dose control member 350rotates along with the drive member 500. Hence, during this procedure,the EOC track follower 900 will retain its position relative to thethread 507 defined by the drive member 500 (see FIG. 4c ).

Finally, after the dose injection has been completed, the injectionbutton 300 is released and the first clutch arrangement C1 is disengagedand the second clutch arrangement C2 is engaged. Again, this has noinfluence on the axial position of the EOC track follower 900 (see FIG.4d ).

After additional subsequent dose setting and dose injection proceduresthe EOC track follower will move gradually in the proximal direction inaccordance with the accumulated dialling up procedures during each ofthe performed administrations. As noted above, at a predetermined pointthe ECO track follower will abut an EOC limitation stop which willprevent further dialling up. Hereby the user is notified that thecartridge does not contain sufficient doses above a certain limit.

As noted above the FIG. 4a shows the device in an initial state beforethe setting of a dose, FIG. 4b shows the device in a state where thedosage selector 200 has been operated to set a particular size of adose, FIG. 4c shows the device in a state where the injection button 300has been pushed down and where the injection of the set dose has beencompleted and, finally, FIG. 4d shows the device in a state aftercompletion of the injection of the set dose and where the injectionbutton 300 has been released.

By comparing the states shown in FIGS. 4a, 4b, 4c and 4d , the movementof each of the clutch arrangements C1, C2, C3 and C4 will becomeevident. Also, in accordance with the above description, the particularmovements of the EOC mechanism and the secondary stop limiter providingthe safety mechanism will become evident.

In the embodiment shown in the figures, the injection device defines apre-filled injection device where a drug filled cartridge is arrangedirremovably within the device. Subsequent to expelling the entireuseable contents of the cartridge the pre-filled injection device isintended to be disposed of and, optionally, be replaced by a newdisposable device. However, in other embodiments being slightlymodified, the injection device may be adapted to be used as a device ofthe durable kind, wherein a first cartridge is replaced by a new onewhen the first cartridge has been emptied.

In line with the invention as set forth above, the invention isgenerally applicable to medical delivery devices, regardless of the kindof administration route for delivering a beneficial agent to the user.Also, the invention may be implemented in both manual injectors wherethe user directly delivers the necessary mechanical energy during thedelivery process as well as spring assisted injectors where apre-stressed or user strained spring in part or fully delivers thenecessary mechanical energy during the delivery process. Further, theinvention may be used in connection with other medical injection deviceswhere actuators having other energy sources than spring actuators areused, such as pneumatically operated actuators having a pneumaticstorage, prime mover actuators having an electrochemical cell storage oreven electrical actuators having an electrical accumulator storage.

In the above description of the exemplary embodiments, the differentstructures providing the desired relations between the differentcomponents just as the means providing the described functionality forthe different components have been described to a degree to which theconcept of the present invention will be apparent to the skilled reader.The detailed construction and specification for the different structuresare considered the object of a normal design procedure performed by theskilled person along the lines set out in the present specification.

The invention claimed is:
 1. A medical injection device for setting andinjecting set doses from a held drug cartridge, comprising: a housingdefining proximal and distal ends, a dose setting arrangement includinga dose setting device that is moved in a first direction away from apredetermined stop in accordance with the size of a set dose and thatmoves back to the predetermined stop during injection of the set dose,the predetermined stop being configured for being fixedly arrangedrelative to the housing, an injection activator adapted to be activatedto inject the set dose, a piston rod adapted to translate relative tothe housing in a distal direction in order to expel a set dose, and arotatable driver coupled to the piston rod and including a stored energysource configured to drive rotation of the driver when the injectionactivator is activated to cause the piston rod to translate relative tothe housing, wherein the stored energy source comprises energysufficient to drive the piston rod for expelling the entire useablecontents of the held drug cartridge, Wherein: the dose setting devicedefines a dose control member configured for rotation around a firstaxis, a first clutch arrangement is arranged between the dose controlmember and the driver, wherein the first clutch arrangement isdisengaged during dose setting so that the dose control member isdisengaged from the driver, and wherein the first clutch arrangementengages by engaging the dose control member with the driver uponactivation of the injection activator to enable the driver to rotate thedose control member while causing the dose setting device to move backtowards the predetermined stop, and a second clutch arrangement arrangedbetween the driver and the housing, wherein the second clutcharrangement is engaged during dose setting so that the driver isprevented from rotating during dose setting, and wherein the secondclutch arrangement disengages upon activation of the injection activatorto enable the driver to rotate relative to the housing.
 2. An injectiondevice as defined in claim 1, wherein the driver defines a drive memberarranged for rotation coaxially with the dose control member, the drivemember having a first track disposed thereon, wherein the dose controlmember has a second track disposed thereon, wherein an end of contenttrack follower is arranged between the drive member and the dose controlmember, the end of content track follower being in engagement with thefirst track and in engagement with the second track, wherein the firsttrack and the second track are configured to cause the end of contenttrack follower to move along the first axis when the dose control memberis rotated relative to the drive member, and wherein the end of contenttrack follower moves towards an end of content stop as the dose settingdevice is dialled up, the end of content stop being arranged at apredefined position to prevent the dose setting device from beingrotated beyond the end of content stop.
 3. An injection device asdefined in claim 2, wherein during injection of the set dose the firstclutch arrangement prevents the drive member from rotating relative tothe dose control member.
 4. An injection device as defined in claim 2,wherein one of the first track and the second track forms a screw threadand wherein the other one of the first track and the second track formsan axial track.
 5. An injection device as defined in claim 2, whereinboth first track and second track form screw threads and wherein thelead of the first track is different than the lead of the second track.6. An injection device as defined in claim 2, wherein at least one ofthe first track and the second track forms a screw thread and whereinthe end of content stop is arranged fixedly relative to the at least onescrew thread.
 7. An injection device as defined in claim 1, wherein thedose control member is axially moved from an inactivated position andinto an activated position upon the injection activator being activatedand wherein the axial position of the dose control member controls thefirst clutch arrangement and the second clutch arrangement.
 8. Aninjection device as defined in claim 1, wherein the injection devicecomprises a dose setting member coupled to the dose setting device foroperating the dose setting device.
 9. An injection device as defined inclaim 8, wherein a third clutch arrangement is arranged between the dosecontrol member and the dose setting member, wherein the third clutcharrangement is engaged during dose setting so that the dose controlmember rotates together with the dose setting member, and wherein thethird clutch arrangement disengages upon activation of the injectionactivator to enable the dose control member to rotate independently fromthe dose setting member.
 10. An injection device as defined in claim 9,wherein the axial position of the dose control member controls the thirdclutch arrangement, and wherein the dose control member is axially movedfrom an inactivated position and into an activated position upon theinjection activator being activated and wherein the axial position ofthe dose control member controls the first clutch arrangement and thesecond clutch arrangement.
 11. An injection device as defined in claim1, wherein at least a piston engaging end of the piston rod extendsalong a second axis, the second axis being offset from the first axis bya distance, wherein the driver comprises a drive nut that rotates aroundthe second axis.
 12. An injection device as defined in claim 1, whereinthe piston rod is a flexible piston rod having a first end extending inparallel with the second axis and adapted to engage a piston of the helddrug cartridge and wherein the second end of the piston rod is adaptedto be flexed away from the second axis.
 13. An injection device asdefined in claim 1, wherein the stored energy source comprises aconstant force spring.
 14. An injection device as defined in claim 13,wherein the constant force spring is arranged in an s-shapedconfiguration between the first and the second axis, and wherein atleast a piston engaging end of the piston rod extends along a secondaxis, the second axis being offset from the first axis by a distance,wherein the driver comprises a drive nut that rotates around the secondaxis.